Router bit question

[jussi]

What are Compression up/down spiral bits used for? What type of cuts? Also they're listed as Up/Down Cut (1+1)Compression and (2+2)Compression. What do the numbers mean?

[scmhogg]

I have a set of upcut that I use on my router table. Good for dadoes and edge planing.

See this: http://www.mlcswoodworking.com/shops...TM25spiral.pdf

Steve

[LCHIEN]

What are Compression up/down spiral bits used for? What type of cuts? Also they're listed as Up/Down Cut (1+1)Compression and (2+2)Compression. What do the numbers mean?

All these directions (up and down) reference the router when held in the handheld position (motor up), not mounted in a table (motor down).

A spiral upcut bit has a spiral flute cut so that it moves the cuttings upwards (e.g. towards the router). THis helps keep dado grooves cleaned out as they cut also makes clean edged (no tearout) cuts on the bottom side of the wood.
A downcut spiral bit has flutes spiraled so as to move the cuttings downwards. THis has the advantage of pushing the material down as its cut to there is less tear out on the cut surface facing the router. When making through cuts with hte router, however, the bottom surface can be more torn out.

A compression bit has two sets of spirals, one up and one down. THis has some of the advantages of up and down cut bits, I think mainly it improves the tearout on both bottom and top surfaces. IT also move material both up and down from the cut, leaving little in the resulting groove.

I'm not sure what the 1+1 or 2+2 designation means, unless there's more sets of flutes... 2+2 being two flutes going up and two flutes going down.

I do know that the flutes actually reduce the material in the bit a great deal. A single flute up or down cut bit is pretty easy to break if you push too hard and are taking more than 1/8" deep bite (with 1/4" spiral bit). I would imagine a compression bit is easier to break yet, multiple flutes 2+2 would be real fragile.

I have used spiral upcut bits and they do the job keeping the grooves clean and reducing tearout. They do break, too. I have not used the compression bits or multi-fluted bits so i'm just repeating what I've read.

[jussi]

Just got clarification from Holbren. It was his ad I saw.

"The UD at the front of the number mean "up and down" spiral or compression bit as they are called. The 2+2 means 2 upcut flutes and 2 downcut flutes. The 1+1 is one of each. "

[Holbren]

1+1 gives faster feed rates on a CNC, 2+2 give a better finish.

[billwmeyer]

Brian,
I bought a couple of your closeout Holbrian Router bits. Quick service and a great price. The plywood sized routerbit set of 2 I had been wanting to get, then there was your ad!

Thanks.

Bill

[crokett]

Interesting thread. Good question and good explanations.

[cabinetman]

The difference between how fast and how clean the machining is done may depend on what the procedure is and how powerful the router is. Some procedures I like doing in a single pass. Others, like flush cutting, choosing between a 2 flute or a 3 flute bit, may depend on the material.
.

[LCHIEN]

MLCS sale on spiral bit set

https://mail.google.com/mail/?shva=1...64cad8451227fa